When people lift weights in a way where they can do 12 reps max, getting stronger is closely tied to getting bigger muscles. But this link isn't seen when lifting for only 4 or 8 reps max.

When people lift lighter weights many times (12 reps max), their muscles get bigger and that's why they get stronger. But when lifting heavier weights fewer times (4-8 reps max), their strength comes more from their brain and nerves learning to use muscles better, not from bigger muscles.

When you lift weights and push yourself almost to the point of not being able to do another rep, you’re more likely to build bigger muscles than if you stop earlier — even if you’re lifting the same weight or doing the same number of sets.

If you want to get stronger, doing your workouts more often helps—more than if you just want to get bigger muscles.

Getting stronger from lifting weights doesn’t always mean your muscles are getting bigger—and vice versa. Strength and size don’t go hand in hand.

If you're a young guy lifting weights more often each week, you'll build more muscle and get stronger—but after a while, your strength stops improving fast, while your muscles keep growing a bit longer.